Didymo in Queenstown Bay

Didymo has been detected in Queenstown Bay in Lake Wakatipu, Biosecurity New Zealand and the Queenstown Lakes District Council announced today.

The organism has previously been detected in other parts of the lake and has been known to bloom on the fringes of lakes where there is sufficient wave action. Didymo has been found in other lakes fed by affected rivers. Four affected rivers flow into Lake Wakatipu. Its main impact is expected to be visual only, though there is obviously a risk of spread.

Didymo response operations manager Jeff Donaldson said Biosecurity New Zealand and the Queenstown Lakes District Council were monitoring the situation, but it was unlikely to have any impact on tourism or tourism operators using the lake.

“At this stage it does not look like the organism will be highly visible in the popular parts of the bay or cause any problems for bathers, particularly on the sandy foreshore, which doesn’t present a good environment for Didymo. It really requires something of more substance to attach to, such as rocks,” Mr Donaldson said.

“Considerable effort has gone into promoting the need for all freshwater users to ‘Check, Clean and Dry’ equipment between waterways, especially over the high use summer period, and that cleaning effort needs to continue regardless of perceived didymo risk. Further signage will be placed in high public use areas,” he said.

“Most operators use equipment dedicated to the lake, and the risk of spread obviously comes when you move equipment between waterways. Those who do move gear should already be cleaning their equipment in line with the ‘Check, Clean and Dry’ procedure we’ve been promoting for the last two years,” Mr Donaldson said.

The information that was gained through monitoring would help inform decisions later about how the bloom in the lake might be best managed. While no control tool for didymo is yet available, environmental trials of a potential chelated copper control tool are to start in Southland next week.

The control tool would not be used until it had been appropriately and scientifically tested, which would take some time. While it had been shown to be effective in a laboratory, the environmental tests were an important step in learning about its effectiveness in the environment, its impacts, and how it might best be used, Mr Donaldson said.

Even if a practical tool was forthcoming, it would not end the need to Check, Clean and Dry equipment, which would remain the best way of limiting the spread of didymo and other aquatic pests, Mr Donaldson said.

To report an exotic pest or disease, call the MAF Emergency Pest and Disease Hotline: 0800 80 99 66.

ENDS

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